Semiconductor device and method of producing the same

ABSTRACT

In a semiconductor device having element isolation made of a trench-type isolating oxide film  13 , large and small dummy patterns  11  of two types, being an active region of a dummy, are located in an isolating region  10 , the large dummy patterns  11   b  are arranged at a position apart from actual patterns  9 , and the small dummy patterns  11   a  are regularly arranged in a gap at around a periphery of the actual patterns  9 , whereby uniformity of an abrading rate is improved at a time of abrading an isolating oxide film  13   a  is improved, and surface flatness of the semiconductor device becomes preferable.

RELATED APPLICATION

This application is a continuation of application Ser. No. 10/342,228 filed on Jan. 15, 2003 now U.S. Pat. No. 6,905,942, which is a divisional of application Ser. No. 09/685,896 filed on Oct. 11, 2000 now U.S. Pat. No. 6,521,969.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor device, in particular, an isolating oxide film in a semiconductor integrated circuit device and a pattern of an electrical active region surrounded by the isolating oxide film.

2. Discussion of Background

In recent years, in accordance with micro miniaturization and high-integration of elements of semiconductor integrated circuit devices, design rules become further specific, and a process becomes very complicated. Especially, in an element isolation, a trench-type isolating oxide film, suitable for micro miniaturization, is widely used. Therefore, it is very important to properly embed the isolating oxide film in a trench without spoiling a performance of an electrical active device region and to polish by a CMP method with high reliability.

FIG. 9 is a plan view of a conventional semiconductor device in which elements are isolated. As illustrated in FIG. 9, a pattern 1 of an electrical active device region, in which elements are formed, is arranged so as to be surrounded by an isolating region 2. Particularly, numerical reference 1 a designates a micro width pattern in the electrical active device region, hereinbelow the micro width pattern is referred to as an actual micro pattern 1 a.

FIGS. 10 a and 10 b are cross-sectional views of the conventional semiconductor device illustrated in FIG. 9, in which semiconductor device the elements are isolated. FIG. 10 a is the cross-sectional view taken along a line A9-A9 in FIG. 9, in which the isolating region 2, being relatively wide, is shown. FIG. 10 b is the cross-sectional view taken along a line B9-B9 in FIG. 9, wherein the actual micro pattern 1 a, which is surrounded by the isolating regions 2 on both of sides, is shown.

An element isolation in a semiconductor device is formed by sequentially arranging an underlayer oxide film 4 and a nitride film 5 on a semiconductor substrate 3. Thereafter, after selectively etching to remove a part of the nitride film 5, to be the isolating region 2, the semiconductor substrate 3 is etched using a mask of the nitride film 5, whereby a trench having a predetermined depth is formed. Succeedingly, after forming an isolating oxide film 7 on an entire surface of the semiconductor substrate 3 so as to fill an inside of the trench 6, the isolating oxide film 7 is abraded by a CMP method to remove the isolating oxide film 7 on the nitride film 5 and leave the isolating oxide film 7 only inside the trench 6, whereby a trench-type isolating oxide film 7 a is formed. The nitride film 5 and the underlayer oxide film 4 are removed after forming the element isolation.

However, the conventional semiconductor device has a problem that an abrading rate is decreased at around a region where the nitride film 5 is formed by an influence of the nitride film 5 because the isolating oxide film 7 on the nitride film 5 is removed by abrasion using a CMP method, the abrading rate of the nitride film 5 is low. On the contrary, in the wide isolating region 2, i.e. the trench-type isolating oxide film 7 a, illustrated in FIG. 10 a, the abrading rate is high, and a sink is produced in a film in its thickness direction by dishing especially in a central portion. Therefore, there are problems that a flatness of a surface is deteriorated, and a later process of patterning using a lithography technique is inappropriately patterned.

Further, as illustrated in FIG. 10 b, when the actual micro pattern 1 a is surrounded by the wide isolating regions 2, i.e. the trench-type isolating oxide films 7 a, there is a case that a part or all of the nitride film 5 of the actual micro pattern 1 a is abraded by overpolishing as illustrated in FIG. 11 because an abrading rate for the trench-type isolating oxide films 7 a is high. Therefore, there are problems that the film thicknesses of the trench-type isolating oxide films 7 a have further large sinks, and electrical characteristics of element are deteriorated such that a threshold value is deteriorated by an inverse narrow channel effect in properties of transistor and a leakage current is increased.

In order to improve the above-mentioned problems, in a conventional technique, a dummy pattern, being an active region of a dummy, is located in the isolating region 2 to improve uniformity of an abrading rate by a CMP method.

FIGS. 12 and 13 are plan views illustrating examples of improvement of conventional semiconductor devices, in which dummy patterns 8, i.e. active regions of a dummy, are arranged in the isolating region 2 of the semiconductor device illustrated in FIG. 9. In FIG. 12, relatively small dummy patterns 8 a are bedded in the isolating region 2. In FIG. 13, relatively large dummy patterns 8 b are bedded in the isolating region 2.

When the isolating oxide film 7 is abraded by the CMP method in a case illustrated in FIG. 12, an abrading rate for a region, where the small dummy patterns 8 a cluster, is lowered. Accordingly, there is a case that the isolating oxide film 7 is left on the nitride film 5 of the dummy pattern 8 a by under-polishing as illustrated in a cross-sectional view of FIG. 14. In this case, not only the isolating oxide film 7 but also the nitride film 5 and an underlayer oxide film 4, which are located on a lower side of the isolating oxide film 7, are not removed by a succeeding removing step, whereby flatness of a surface is extremely spoiled, and it becomes difficult to pattern in a later step.

Further, in the case illustrated in FIG. 13, because the dummy patterns 8 b are large, there are areas where the dummy patterns are not arranged in a periphery of the actual pattern 1. Especially, when the dummy patterns 8 b do not exist in the periphery of the actual micro pattern 1 a, a cross-sectional view taken along a line B13-B13 is similar to that in FIG. 10 b. As illustrated in FIG. 11, because of the high abrading rate or the trench-type isolating oxide films 7 a, there is a case that a part or all of the nitride film 5 of the actual micro pattern 1 a is abraded by over-polishing. Therefore, as described above, the sinks in the trench-type isolating oxide films 7 a become further large, whereby electrical characteristics of element are deteriorated.

SUMMARY OF THE INVENTION

It is an object of the present invention to solve the above-mentioned problems inherent in the conventional technique and to provide a semiconductor device with an element isolation, made of a trench-type isolating oxide film formed in an isolating region, wherein over-polishing and under-polishing are restricted by improving uniformity of an abrading rate at time of abrading the isolating oxide film by a CMP method, whereby the semiconductor device has a preferable surface flatness and high reliability.

According to a first aspect of the present invention, there is provided a semiconductor device comprising:

a semiconductor substrate;

electrical active device regions formed in the semiconductor substrate; and

an isolating region made of a trench-type isolating oxide film, of which surface is abraded by a CMP method,

wherein a plurality of types of dummy patterns having various areas, being active regions of a dummy surrounded by the trench-type isolating oxide film patterns, are located in the isolating region so that the trench-type isolating oxide film pattern does not exceed a predetermined width, and

the dummy patterns are regularly arranged by setting an area in response to a positional relationship between the dummy patterns and patterns of the electrical active device regions.

According to a second aspect of the present invention, there is provided the semiconductor device according to the first aspect of the invention,

wherein relatively large dummy patterns are arranged from a position apart from the electrical active device patterns to the electrical active device patterns, and

relatively small dummy patterns are inserted in a gap around the electrical active device pattern.

According to a third aspect of the present invention, there is provided the semiconductor device according to the first aspect of the invention,

wherein dummy patterns having relatively small areas are arranged around the electrical active device patterns, and

dummy patterns having relatively large areas are arranged around the dummy patterns having the relatively small areas.

According to a fourth aspect of the present invention, there is provided the semiconductor device according to the first through third aspects of the invention,

wherein dummy patterns are arranged on both sides of micro width patterns of an electrical active device interposing the trench-type isolating oxide film patterns, and

the widths of the trench-type isolating oxide film patterns are about one through ten times of the micro width pattern.

According to a fifth aspect of the present invention, there is provided a method of producing the semiconductor device comprising:

a first step of forming a trench of a predetermined depth in a predetermined region in an isolating region after forming a nitride film on a semiconductor substrate interposing an oxide film, and forming a trench region and an active region of a dummy, to be a dummy pattern, in the isolating region;

a second step of depositing an isolating oxide film on an entire surface so as to fill the trench;

a third step of selectively etching to leave the isolating oxide film larger than predetermined pattern dimensions in a dummy pattern region so as to have a predetermined width in an end region of the pattern; and

a fourth step of abrading to remove the isolating oxide film in the nitride film by a CMP method.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanied drawings, wherein:

FIG. 1 is a plan view of a semiconductor device according to Embodiment 1 of the present invention;

FIG. 2 a is a cross-sectional view of the semiconductor device according to Embodiment 1 of the present invention;

FIG. 2 b is a cross-sectional view of the semiconductor device according to Embodiment 1 of the present invention;

FIG. 3 a is a cross-sectional view for illustrating a method of producing the semiconductor device according to Embodiment 1 of the present invention;

FIG. 3 b is a cross-sectional view for illustrating the method of producing the semiconductor device according to Embodiment 1 of the present invention;

FIG. 3 c is a cross-sectional view for illustrating the method of producing the semiconductor device according to Embodiment 1 of the present invention;

FIG. 4 a is a cross-sectional view for illustrating a method of producing the semiconductor device according to Embodiment 1 of the present invention;

FIG. 4 b is a cross-sectional view for illustrating the method of producing the semiconductor device according to Embodiment 1 of the present invention;

FIG. 4 c is a cross-sectional view for illustrating the method of producing the semiconductor device according to Embodiment 1 of the present invention;

FIG. 5 a is a cross-sectional view for illustrating a method of producing a semiconductor device according to Embodiment 2 of the present invention;

FIG. 5 b is a cross-sectional view for illustrating the method of producing the semiconductor device according to Embodiment 2 of the present invention;

FIG. 5 c is a cross-sectional view for illustrating the method of producing the semiconductor device according to Embodiment 2 of the present invention;

FIG. 6 a is a cross-sectional view for illustrating a method of producing the semiconductor device according to Embodiment 2 of the present invention;

FIG. 6 b is a cross-sectional view for illustrating the method of producing the semiconductor device according to Embodiment 2 of the present invention;

FIG. 6 c is a cross-sectional view for illustrating the method of producing the semiconductor device according to Embodiment 2 of the present invention;

FIG. 7 is a plan view of a semiconductor according to Embodiment 3 of the present invention;

FIG. 8 a is a cross-sectional view of the semiconductor device illustrated in FIG. 7;

FIG. 8 b is a cross-sectional view of the semiconductor device illustrated in FIG. 7;

FIG. 9 is a plan view of a conventional semiconductor device;

FIG. 10 a is a cross-sectional view of the conventional semiconductor device;

FIG. 10 b is a cross-sectional view of the conventional semiconductor device;

FIG. 11 is a cross-sectional view for illustrating problems in the conventional semiconductor device;

FIG. 12 is a plan view of another conventional semiconductor device;

FIG. 13 is a plan view of another conventional semiconductor device; and

FIG. 14 is a cross-sectional view of the semiconductor device illustrated in FIG. 12.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A detailed explanation will be given of preferred embodiments of the present invention in reference to FIGS. 1 through 8 b as follows, wherein the same numerical references are used for the same or similar portions and descriptions of these portions is omitted.

EMBODIMENT 1

Hereinbelow, Embodiment 1 of the present invention will be described in reference of figures.

FIG. 1 is a plan view of a semiconductor device according to Embodiment 1 of the present invention. FIG. 2 a is a cross-sectional view of semiconductor device taken along a line A1-A1 in FIG. 1. FIG. 2 b is a cross-sectional view of semiconductor device taken along a line B1-B1. In the figures, numerical reference 9 designates a pattern, hereinbelow referred to as an actual pattern 9, of an electric active device region, in which elements are formed, wherein the actual patterns 9 are surrounded by an isolating region 10. Particularly, numerical reference 9 a designates a micro width pattern, hereinbelow referred to as an actual micro pattern 9 a, of the electric active device region. Numerical reference 11 designates a dummy pattern being an active region of a dummy arranged inside the isolating region 10. Numerical reference 11 a designates a relatively small dummy pattern. Numerical reference 11 b designates a relatively large dummy pattern. Numerical reference 12 designates a semiconductor substrate, and numerical reference 13 designates a trench-type isolating oxide film.

As illustrated in FIGS. 1 through 2 b, the dummy patterns 11 of two types, i.e. the dummy patterns 11 a and 11 b, having different areas are arranged in the isolating region surrounding the actual pattern 9. The dummy patterns 11 are arranged such that the large dummy patterns 11 b are regularly arranged from a region apart from the actual pattern 9 to a neighbor of the actual pattern 9 so as to be bedded. For example, dummy patterns 11 b of a 18 μm square are arranged at a pitch of 20 μm. In a periphery of the actual pattern 9, which is a gap where the large dummy patterns 11 b are not arranged, the small dummy patterns 11 a are inserted and regularly arranged. For example, dummy patterns 11 a of a 3 μm square are arranged at a pitch of 5 μm.

A step of isolating elements in the semiconductor device will be described in reference of FIGS. 3 a through 4 c. FIGS. 3 a through 3 c are cross-sectional views of a portion illustrated in FIG. 2 a for illustrating a manufacturing process thereof. FIGS. 4 a through 4 c are cross-sectional views of a portion illustrated in FIG. 2 b for illustrating a manufacturing process thereof.

At first, an underlayer oxide film 14, for example, of a film thickness of about 10 nm, is formed on the semiconductor substrate including a p-type single crystal silicon having a specific resistance of, for example, 10 Ω·Cm. Further, a nitride film 15 of a film thickness of about 0.1 μm is further formed. Thereafter, after selectively etching to remove a portion of the nitride film 15 other than active regions 9 and 11 in the actual pattern 9 and the dummy patterns 11, the semiconductor substrate 12 is etched in a depth direction by about 0.3 μm using a mask of the nitride film 15, whereby the trench 16 is formed. Succeedingly, an inside of the trench 16 is buried, and an isolating oxide film 13 a having a film thickness of, for example, about 0.4 μm including high density plasma (HDP) oxide film is deposited on an entire surface. Thereafter, a resist pattern 17 is formed on the isolating oxide film 13 a to etch the isolating oxide film 13 a in the active regions 9 and 11, wherein the resist pattern 17 is larger than a predetermined dimensions of the pattern. The resist pattern 17 is undersized by, for example, about 1.5 μm with respect to the active regions 9 and 11 to be processed as illustrated in FIGS. 3 a and 4 a.

In the next, the isolating oxide film 13 a is etched to be opened to reach the nitride film 15 using the resist pattern 17 as a mask. Accordingly, the relatively wide active regions 9 and 11, i.e. the isolating oxide film 13 a on the region of the large dummy patterns 11 b and the relatively wide actual pattern 9 is opened at a central portion thereof, whereby only end portions 13 b are left. The etching may be a dry-etching or a wet-etching. An HDP oxide film 13 c formed on the actual micro pattern 9 a is shaped like a small triangle as illustrated in FIGS. 3 a through 4 c. For example, in a clustered region of the actual micro pattern 9 a, such as a memory cell of a DRAM portion, are a large number of the HDP oxide films 13 c of the small rectangular shape are clustered as in FIGS. 3 b and 4 b.

In the next, the isolating oxide film 13 a is abraded by a CMP method, the isolating oxide film 13 a on the nitride film 15 is removed, and the isolating oxide film 13 a is left only in the trench 16, whereby the trench-type isolating oxide film 13 is formed as illustrated in FIGS. 3 c and 4 c.

In the next, the nitride film 15 and the underlayer oxide film 14 are sequentially removed by wet-etching, and a predetermined process is provided, whereby the element isolation illustrated in FIGS. 2 a and 2 b is completed.

In Embodiment 1, the large dummy patterns 11 b are regularly arranged from the region apart from the actual pattern 9 so as to bed thereon, and the small dummy patterns 11 a are regularly arranged so as to be inserted in the region of the gap around the actual pattern 9 where the large dummy patterns 11 b can not be arranged. Accordingly, the width of the trench-type isolating oxide film 13 does not exceed the predetermined width. Therefore, it is possible to suppress an increment of the abrading rate when the isolating oxide film 13 a is abraded by the CMP method, whereby a sink of the film in the thickness direction by dishing can be prevented.

Further, because the width of the trench-type isolating oxide film 13 on the both sides of the actual micro pattern 9 a can be reduced by inserting the small dummy patterns 11 a, it is possible to prevent abrasion of the nitride film 15 of the actual micro pattern 9 a caused by overpolishing, and a sink of the film in its thickness direction of the adjacent trench-type isolating oxide film 13 a can be prevented, whereby a drop of a threshold value by an adverse narrow channel effect in properties of transistor, and deterioration of electrical characteristics of elements, such as an increment of a leakage current, can be prevented. The width of the trench-type isolating oxide film 13 on the both sides of the actual micro pattern 9 a is preferably about one through ten times of that of the actual micro pattern 9 a, wherein uniformity of the abrading rate by the CMP method is improved, and the above-mentioned effects are securely obtainable.

Further, by arranging the large dummy patterns 11 b and the small dummy patterns 11 a, the small dummy patterns 11 a are not partly clustered, whereby the uniformity of the abrading rate by the CMP method is improved, and it is possible to prevent the isolating oxide film 13 a from remaining on the nitride film by underpolishing. The isolating oxide film 13 a on the large dummy patterns 11 b and the relatively wide actual pattern 9 as the opening at the center thereof by pre-etching performed before the abrading step by the CMP method, whereby the isolating oxide film 13 a is easily abraded, and problems caused by underpolishing do not occur.

Further, a dominating ratio of the dummy patterns 11 and the isolating oxide film 13 a of the active regions 9 and 11 with respect to an entire area is in a range of about 50 through 80%, which is in a level similar to that in the region where the actual patterns 9 are clustered. Accordingly, uniformity of the abrading rate by the CMP method is further improved on an entire surface of the semiconductor substrate 12.

As described, in Embodiment 1, because the uniformity of the abrading rate is improved when the isolating oxide film 13 a is abraded by the CMP method when the elements are isolated, it is possible to obtain the semiconductor device with preferable surface flatness and high reliability.

The dimensions of the small dummy patterns 11 a are appropriately set within a range of 1 through 100 times of the minimum dimensions of the actual patterns 9. The dimensions of the large dummy patterns 11 b are appropriately set within a range of 10 through 1,000 times of the minimum dimension of the actual patterns 9. The dummy patterns 11, i.e. the small dummy patterns 11 a and the large dummy patterns 11 b, may be shaped like not only a rectangular but also a strap, a hook, and lines and spaces as long as the dummy patterns are regularly arranged to facilitate a control of process.

Further, although the resist pattern 17 being a pre-etching mask for the isolating oxide film 13 a is under-sized by about 1.5 μm with respect to the active region of the resist pattern 17 being the pre-etching mask, the extent of the undersize is not limited thereto as long as the isolating oxide film 13 a is left in the end portions of active region after pre-etching.

Further, although the isolating oxide film 13 a is pre-etched to the surface of the nitride film 15, it is possible to stop the pre-etching before reaching the surface and succeedingly adjust etching in the abrading step by the CMP method.

EMBODIMENT 2

In the next, a structure that the element isolation of the semiconductor illustrated in FIGS. 1 through 2 b according to Embodiment 1 is realized using a TEOS oxide film as an isolating oxide film will be described below in reference of FIGS. 5 a through 6 c.

FIGS. 5 a through 5 c illustrate cross-sectional views of a portion corresponding to that in FIG. 2 a. FIGS. 6 a through 6 c illustrate cross-sectional views of a portion corresponding to that in FIG. 2 b for explaining element isolating steps.

In a similar manner to that in Embodiment 1, after forming an underlayer oxide film 14 and a nitride film 15 on the semiconductor substrate 12, a part of the oxide film other than an actual patterns 9 and an active region 9 of dummy patterns 11 is selectively etched to remove, and a trench 16 is formed on the semiconductor substrate 12 using a mask of the nitride film 15.

Succeedingly, after depositing an isolating oxide film 13 d made of a TEOS oxide film on an entire surface so as to embed an inside of the trench 16, a resist pattern 17 a is formed on the isolating oxide film 13 d. The resist pattern 17 a is formed as a mask pattern for etching the isolating oxide film 13 d in a region where actual micro patterns 9 a, such as the active regions 9 and 11, being larger than predetermined pattern dimensions and memory cells in a DRAM portion cluster, wherein the resist pattern 17 a is under-sized by, for example, about 1.5 μm with respect to a region to be processed, as illustrated in FIGS. 5 a and 6 a.

In the next, the isolating oxide film 13 d is etched to open in a predetermined depth, where a surface of the nitride film 15 is not exposed, using the resist pattern 17 a as the mask. Accordingly, the relatively wide active regions 9 and 11, i.e. the isolating oxide film 13 d in a region where the large dummy patterns 11 b, the relatively wide actual patterns 9, and the actual micro patterns 9 a are clustered, are opened to an extent that the underlayer nitride film 15 is not exposed at a central portion, whereby an end portion 13 e is left. The etching may be dry-etching or wet-etching as in FIGS. 5 b and 6 b. Thereafter, in a similar manner to that in Embodiment 1, the isolating oxide film 13 d is abraded by a CMP method to remove a part of the isolating oxide film 13 d on the nitride film 15 and leave the isolating oxide film 13 d only inside the trench 16, whereby a trench-type isolating oxide film 13 is formed as illustrated in FIGS. 5 c and 6 c.

In the next, the nitride film 15 and the under layer oxide film 14 are sequentially removed by wet-etching, and provided with a predetermined process, whereby the element isolation illustrated in FIGS. 2 a and 2 b is completed.

In Embodiment 2, in a manner similar to Embodiment 1, because uniformity of the abrading rate is improved at time of abrading the isolating oxide film 13 d for forming the element isolation by the CMP method, it is possible to obtain a semiconductor device having preferable surface flatness and high reliability.

Further, the isolating oxide film 13 d made of the TEOS oxide film is subjected to pre-etching not only in the relatively wide active regions 9 and 11 but also in the region with the clustered actual micro patterns 9 a. This is because, the film thickness of the TEOS oxide film 13 d is not decreased on the actual micro patterns 9 a, the TEOS oxide film 13 d on the actual micro patterns 9 a has a large area by extending to an upper layer of adjacent trenches 16 in the region with the clustered actual micro patterns 9 a, and therefore underpolishing is apt to occur at time of abrading by the CMP method.

EMBODIMENT 3

In the next, Embodiment 3 of the present invention will be described.

FIG. 7 is a plan view of a semiconductor device according to Embodiment 3 of the present invention. FIG. 8 a is a cross-sectional view taken along a ling A7-A7 in FIG. 7. FIG. 8 b is a cross-sectional view taken along a ling B7-B7 in FIG. 7.

As illustrated in the figures, two types of dummy patterns 11, i.e. 11 a and 11 b, having different areas are arranged in an isolating region 10 surrounding actual patterns 9. The dummy patterns 11 are arranged such that the small dummy patterns 11 a are regularly arranged in a periphery of the actual patterns 9, for example, dummy patterns 11 a of a 3 μm square is arranged at a pitch of 5 μm.

In a periphery of the actual patterns 9 and the small dummy patterns 11 a surrounding the actual pattern 9, the large dummy patterns 11 b are regularly arranged so as to be bedded. For example, dummy patterns 11 b of a 18 μm square are arranged at a pitch of 20 μm.

An element isolating process of the semiconductor device is conducted in a manner similar to that in Embodiment 1 when an HDP oxide film 13 a is used as the isolating oxide film as illustrated in FIGS. 3 a through 4 c, or in a manner similar to that in Embodiment 2 when the TEOS oxide film 13 d is used as the isolating oxide film as illustrated in FIGS. 5 a through 6 c.

In Embodiment 3, because the small dummy patterns 11 a are arranged in the periphery of the actual patterns 9, and the large dummy patterns 11 b are regularly arranged around the small dummy patterns 11 a, the width of a trench-type isolating oxide film 13 does not exceed a predetermined width. Therefore, when an isolating oxide film 13 a and/or 13 d is abraded by a CMP method, it is possible to suppress an increment of an abrading rate, and prevent a sink of a film thickness by dishing.

Further, because the width of the trench-type isolating oxide film 13 on the both sides of the actual micro pattern 9 a is made small because the small dummy patterns 11 a are arranged in the periphery thereof, it is possible to prevent the nitride film 15 of the actual micro patterns 9 a from being abraded by overpolishing, whereby electrical characteristics of element are not deteriorated. Further, by arranging the large dummy patterns 11 b and the small dummy patterns 11 a, the small dummy patterns 11 a are not clustered, and underpolishing is prevented. The isolating oxide film 13 a and/or 13 d on a region of the large dummy patterns 11 b and the relatively wide actual patterns 9 as an opening at a central portion thereof by pre-etching performed before the abrading step by the CMP method, whereby it is possible to easily abrade, and problems caused by the underpolishing can be prevented.

As described, in Embodiment 3, as in Embodiments 1 and 2, because uniformity of the abrading rate is improved when the isolating oxide film 13 a and/or 13 d is abraded by the CMP method at time of isolating elements, a semiconductor device with preferable surface flatness and high reliability is obtainable.

In Embodiments 1 through 3, the two types of the dummy patterns 11, which are large and small, are used. However, the types may be three or more. In this case, as in Embodiment 1, the largest dummy patterns 11 are arranged at a position apart from an actual pattern 9, and smaller dummy patterns 11 are arranged toward the actual pattern 9, or as in Embodiment 3, the smallest dummy patterns 11 is arranged in a periphery of an actual pattern 9, and larger dummy patterns 11 are arranged toward a position apart from the actual pattern.

As such, by setting areas of the dummy patterns 11 in accordance with positional relationships between the actual patterns 9 and the dummy patterns 11 for an arrangement, and suppressing an unnecessary increment of the width of the trench-type isolating oxide film 13, the uniformity of the abrading rate is improved at time of abrading the isolating oxide films 13 a and/or 13 d, and the semiconductor device with preferable surface flatness and high reliability is obtainable.

The first advantage of the semiconductor device according to the present invention is that uniformity of an abrading rate can be improved at time of abrading the isolating oxide film by a CMP method, surface flatness is preferable, and reliability becomes high.

The second advantage of the semiconductor device according to the present invention is that electrical characteristics of elements are not deteriorated, and simultaneously surface flatness becomes preferable and reliability is high.

Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.

The entire disclosure of Japanese Patent Application No. 11-355645 filed on Dec. 15, 1999 including specification, claims, drawings and summary are incorporated herein by reference in its entirety. 

1. A semiconductor device comprising: a semiconductor substrate; an active device region formed on a principal surface of the semiconductor substrate; an isolating region surrounding the active device region; a plurality of first dummy patterns arranged regularly in rows and columns at a first pitch in the isolating region; and a plurality of second dummy patterns arranged regularly in rows and columns at a second pitch in the isolating region, wherein the second pitch is larger than the first pitch, and wherein each of the second dummy patterns has a larger area than each of the first dummy patterns.
 2. The semiconductor device according to claim 1, the isolating region is made of an oxide film buried in a ditch formed on the principal surface of the semiconductor substrate.
 3. The semiconductor device according to claim 2, each of the first dummy patterns and each of the second dummy patterns are surrounded with the oxide film.
 4. The semiconductor device according to claim 1, the active device region is arranged in the vicinity of the first dummy patterns rather than the second dummy patterns.
 5. A semiconductor device comprising: a semiconductor substrate; two active device regions formed on a principal surface of the semiconductor substrate; an isolating region formed between two active device regions; a plurality of first dummy patterns arranged regularly in rows and columns at a first pitch in the isolating region; and a plurality of second dummy patterns arranged regularly in rows and columns at a second pitch in the isolating region; wherein the second pitch is larger than the first pitch, and wherein each of the second dummy patterns has a larger area than each of the first dummy patterns.
 6. The semiconductor device according to claim 5, the isolating region is made of an oxide film buried in a ditch formed on the principal surface of the semiconductor substrate.
 7. The semiconductor device according to claim 6, wherein each of the first dummy patterns and each of the second dummy patterns are surrounded with the oxide film. 